The invention relates to a method for operating a motor vehicle during the operation of a fully automatic driver assistance system designed to guide the vehicle independently of the driver.
Various vehicle manufacturers are currently developing fully automatic systems designed to guide vehicles independently of drivers and which are intended to relieve drivers from driving workload during certain traffic situations by having the driving task performed fully automatically. One example would be traffic jam assistant, which can be used during traffic jam situations on highways. In this example, both longitudinal guidance (analogous to a distance-based or active cruise control) and transversal guidance for keeping the vehicle within the lane are performed automatically below a predefined speed limit of, for example, 60 km/h or 40 km/h. A particular embodiment of traffic jam assistants of this type would even permit the driver to remove his hands from the steering wheel for a certain period of time.
Fully automatic driver assistance systems designed for guiding the vehicle independently of the driver demand high safety requirements, since the occurrence of a fault would put both the driver and the other traffic participants at high risk.
A method for operating a driver assistance system of this type is already known from DE 10 2010 021 591 A1 in which a plausibility monitoring module continually checks whether a fault is present. Faults are defined as various situations such as, for example, the vehicle driving too fast or driving backwards, a specified minimum distance in relation to a vehicle ahead not being maintained and/or the vehicle leaving the lane. If such a fault is detected, a driving intervention serving to transfer the motor vehicle into a safer state is at least performed.
The invention seeks to solve the problem of providing a better method, with regard to detecting critical traffic situations and initiating appropriate measures, for operating a motor vehicle while a fully automatic driver assistance system designed for guiding the vehicle independently of the driver is operating.
Advantageous additional embodiments can be found in the subordinate claims.
In principle, the invention assumes a method for operating a motor vehicle while a fully automatic driver assistance system designed for guiding the vehicle independently of the driver is operating. Driver assistance systems of this type are designed such that they can actuate by means of one or more control units the actuation units of a (electrically powered) steering system and/or the actuation units of a drive system and/or a brake system when predefined basic conditions are present—e.g., when driving on a highway or at a speed below a predefined speed limit, such that the vehicle is guided or held within its detected driving lane and taking into consideration a vehicle ahead or a preceding vehicle detected as target object and any further traffic participants. In this case longitudinal guidance can be provided in the same manner as the longitudinal guidance of a distance-based cruise control (ACC).
The fundamental idea of the invention is now that in situations in which the vehicle's driving lane possibly ceases to exist or in situations in which a departure from the driving lane of the vehicle ahead is falsely recognized due to an incorrectly detected lane marking, intervention is made in the driver assistance system control such that no hazardous situations for the driver or other traffic participants can arise. To ensure that this requirement is met, the method according to the invention sets itself apart by the fact that a braking action is undertaken upon the vehicle ahead detected as a target object leaving the recognized own driving lane and there being no new preceding vehicle ahead. Through this measure, it can be ensured that if, for example, the own driving lane ends or an obstacle is present in the driving lane and is not detected that the vehicle will not leave the driving surface or collide with the obstacle as a result of a corresponding actuation of the drive unit.
In such situations a braking action is advantageously performed such that the vehicle comes to a standstill within a predefined time interval or within a predefined distance should the driver himself not resume the driving task or actively intervene in vehicle control during the braking procedure. To prevent a departure from the road or a collision with an obstacle, a braking action is performed such that the vehicle comes to a standstill within the distance existing between the motor vehicle and the vehicle ahead at the point in time at which the departure of the vehicle ahead detected as target object from the lane was detected, i.e. the motor vehicle will come to a stop no later than at the position where the target object ahead left the lane.
Because a braking action of this type is in principle required only if the driver is distracted at the time and does not recognize the possibly impending danger, the method according to the invention can be advantageously refined such that a corresponding braking action is performed only if upon the target object departing from the driving lane it is simultaneously detected that the driver is currently not resuming the driving task or is not able to do so immediately. This can in turn be detected or assumed if it is established that the driver is not touching the steering wheel, i.e. does not have his hands on the steering wheel.
To be able to alert the driver to this special situation, the driver is advantageously issued, simultaneously with the corresponding braking action, an optical, acoustical or haptic warning signal with a message prompting him to resume control of the vehicle. The warning can also be issued prior to the braking action if necessary.
With regard to transversal control of the vehicle following the detection of the departure from the recognized driving lane of the target object, various measures can be taken. According to a first alternative, the steering actuator units of the steering system can be actuated such that the vehicle continues to be guided along a transversal control requirement or transversal control trajectory determined or required on the basis of the fully automatic driver assistance system designed to guide the vehicle independently of the driver, i.e. the vehicle continues to be held within the lane or in the center of the lane. Alternatively, according to an advantageous refinement of the invention, the steering actuator units of the steering system can be actuated such that the vehicle, upon detection of the target object ahead leaving its own driving lane, is guided alone a newly determined transversal control fallback trajectory. For example, it could be expedient in this case to bring the vehicle to a standstill at the right or left edge of its own driving lane.
The invention is described again in greater detail on the basis of the exemplary embodiment presented below. Illustrated are other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.